Ch43P35-L4 Atypical Catagen-like 

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F1Ch43 (G4879): This is a small compact lesion. the basic features are acceptable in the category of follicular hamartomas of the butterfly area of the face. There is mild papillomatosis. In a solid portion to the left, there are numerous whorls. To the right the epithelium is mostly intact and there is a prominence of cells of the superficial unit-like type. Centrally, above the center of the field, small whorls are numerous; they are separated from the neighbors by empty, lytic defects. From the fibrous tissue on the right, new fibrous tissue has extended into, and filled, some of the defects. The pattern is that of sclerosing entrapment.


F2Ch43: This is the left extremity of the lesion. In this field, a follicle-like component marks the limits; its lumen is dilated and contains compact keratinized debris; granular cells are prominent. There are numerous whorls. In moving to the right, there is an increased prominence of lytic defects among the small whorls. Flatterned cells are present at the interface between some of the whorls and the defects; these cells might be either keratinocytes, or migrant fibroblasts. Near the top of the field, on the right, many of the cells of superficial unit-like type have vacuolated cytoplasms. There are scattered dyskeratotic cells.


F3Ch43: This is representative of the central portion of the lesion. The tendency for the lytic process to affect the domain among the whorls is illustrated. Many of the cells in the domain among the whorls are vacuolated but are not of basal unit-like type. A basal unit-like component and a basal layer are not evident; the lytic process clearly is to blame but the sequence is uncertain. It is possible that the basal unit-like component first gives itself over to a transformation in which all of the cells are committed to terminal differentiation. The lytic process then eliminates the domain among the whorls. The effects of the process are something akin to those of a lichenoid reaction but are mediated in the absence of inflammatory cells. The process can be embraced in the broad definition of the apoptosis. It can also be characterized as neoplastically committed catagen-like phenomena; in this approach, the non-specific cytologic features of squamous epithelium can be accepted as being of a type seen in a catagen process, as it affects the inconstant portion of a follicle.


F4Ch43: This is the right side of the lesion. Many of the changes have been commented on. The epithelium below the keratin-filled lumen has features of a distorted whorl. In the distorted whorl, there are scattered dyskeratotic cells. Some of the cells have small cytoplasmic vaculoes. Many of the cells are granular cells. The cells of this area, and in the hyperplastic epidermis to the right are of superficial unit-like type. The distorted whorl has defined a sharp interface with the adjacent epithelium. The keratinized debris in the lumen can be easily dismissed as a follicular plug; on the other hand, whorls of keratinized debris are identifiable; it would appear that the central debris of more than one whorl has been extruded at the surface.


F5Ch43: The patterns in the “plug,” in part, can be characterized as whorls of keratinized debris; in the formation of the lumen, some of the whorls of cells have been sacrificed and eliminated.


F6Ch43: The distorted whorl is again represented. The features have been described.


F7Ch43: Atypia is uniform, and moderately severe. Nuclei vary in size, and outline; nucleoli are prominent. Whorls and a background domain are represented. There are scattered atypical, dyskeratotic cells. In the background component, many of the cells are vacuolated. There are scattered, small lytic clefts, especially to the left.


F8Ch43: Sclerosing entrapment is well developed. A basal layer is not a feature of any of the whorls. Dead, dyskeratotic keratinocytes are being shed into the fibrous tissue at the periphery of some of the whorls. The stroma retains the distinctive qualities seen in the process of sclerosing entrapment; the stroma does not show the qualities of the reactive stroma seen in response to a common squamous cell carcinoma. The lesion has been cut across at the base. This lesion qualifies as an atypical, catagen-like tricholemmoma (a variant of so called “inverted follicular keratosis”). It should be completely excised.


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